Liquid fuel burners



y 1969 1. B. CAMPBELL 3,446,439

- LIQUID FUEL BURNERS Filed Feb. 20. 1967 3,446,439 LIQUID FUEL BURNERSCampbell, Dumbartonshire, Scotland, assignor to Babcock 8: Wilcox,Limited, London,

Iain Brown England, a company of Great Britain Filed Feb. 20, 1967, Ser.No. 618,565 Claims priority, application Great Britain, Feb. 22, 1966,7,705/ 66 Int. Cl. F23d 13/40, 15/00 US. Cl. 239419.3 6 Claims ABSTRACTOF THE DISCLOSURE This invention relates to liquid fuel burners and,more particularly, to a liquid fuel burner arranged to be positioned inan air register which supplies air in a flow substantially parallel tothe burner axis, an impellor plate with circumferentially spacedopenings is positioned adjacent the burner head to impart a degree ofwhirl to the combustion air being supplied to an atomized spray ofliquid fuel discharged from the burner head.

British patent specification No. 579,591 describes an atomizercomprising a barrel at the end of which is provided a sprayer platewhich has an imperforate central part and which is formed with passagesof circular crosssection diverging from an inner space adapted to be fedwith elastic fluid and directed with their longitudinal axes lying onand spaced around a frustrum of a cone and other passages also ofcircular cross-section respectively making junctures with the firstpassages at locations remote from the outlets thereof and extending froman outer space adapted to be fed with liquid fuel.

However, it has been found that, at least in instances in which air isdischarged at a high velocity from the register without a pronounceddegree of swirl, that upon igniting the atomized spray of liquid fuelfrom an adjacent burner the resultant flame tends to develop at anappreciable distance from the burner head, which can, at times, bedisadvantageous.

According to the present invention there is provided an atomizer headfor a liquid fuel burner including mixing chambers distributed aroundthe central axis of the head with their longitudinal axes diverging inthe general direction of discharge, each chamber being provided with aninlet duct for liquid fuel and an inlet duct for elastic atomizing fluidarranged to connect with spaces defined by co-axial tubes in a barrelportion of the liquid fuel burner, wherein the atomizer head is formedwith a central passage of circular cross-section discharging elasticatomizing fluid along the central axis of the atomizer head.

The provision of a dicharge along the axis of the atomizer head centralof the spray cone of atomized liquid fuel tends to assist in theestablishment of a stable flame at a burner upon ignition of the sprayof atomized fuel from an adjacent burner and also tends to preventdeposition of carbon on the atomizer head during operation.

3,446,439 Patented May 27, 1969 The invention will now be described byway of example with reference to the accompanying drawings, in which:

FIGURE 1 is a sectional side elevation of an oil burner together with anassociated impellor and air register and which shows a portion of thewall of a furnace chamber;

FIGURE 2 is a sectional side elevation of an atomizer head and part of abarrel at the front of the oil burner; and

FIGURE 3 is a front elevation corresponding to FIG- URE 2.

Referring to FIGURE 1, there is shown an oil burner 2 disposed axiallyof a burner opening 4 in an associated furnace wall 6, the outer end ofthe opening communicating with an air register 8 provided in an air box10 mounted on the furnace chamber wall. An impellor 12 is mounted on adistance piece tube 14 adjacent the forward end of the oil burner and isformed with circumferentially spaced openings through which a centralportion of the combustion air is admitted to the spray of atomized oilupon discharge thereof from the forward end of the oil burner, the airpassing through the impellor 12 being circumferentially deflected byblades of the impellor. The distance piece tube 14 is mounted on a tailpiece 16 coupled by a yoke 18 to a rear portion 20 of the oil burner.The tail piece 16 is formed with inlet connections (not shown)communicating respectively with a steam passage 22 and an oil passage 24in the rear end portion 20. A burner barrel including inner and outerco-axially disposed tubes 26, 28, with the inner tube 26 threaded intothe rear end portion 20 and communicating with the steam passage 22 andthe outer tube 28 movably sealed to, the rear end portion 20, forexample, in a manner similar to that described in British patentspecification No. 891,195, and the space intermediate the inner andouter tubes in communication with the oil supply passage 24.

Referring now to FIGURES 2 and 3, an atomizer head 30 of cylindricalform has an internally threaded, central, well portion 32 formed with anannular seat 34 at the rearward end face thereof is screwed onto theforward end of the inner tube 26 to compress a gasket 36 between theannular seat 34 and a complementary seat 38 provided on a collar 40, toform a leak-tight joint. An outer, circumferential, flange 42 on theatomizer head is formed with an annular seat 44 at the rearward facethereof and compresses a gasket 46 against a complementary seat 48formed on the forward end face of the outer tube 28 by the action of acap nut 50 co-acting with an external thread on the forward end of thetube 28 and bearing against a shoulder 52 on the atomizer head to form aleak-tight joint between the atomizer head and the outer tube. Afrusto-conical surface 54 formed as a chamfer on the front end of theatomizer head is penetrated perpendicu larly by seven, equiangularlyspaced, stepped bores 56 communicating with a conical forward end 58 ofthe well portion. A second frusto-conical surface 60 is provided at therear end of the atomizer head and is penetrated perpendicularly withbores 62 connecting respective stepped bores 56, at the part of largerdiameter thereof, with the space intermediate the inner and outer tubes26, 28. The front end of the atomizer head is penetrated by a single,central bore 64, also of stepped form, communicating with the conicalforward end 58 of the well portion at the apex thereof. A third surface66 in the form of a short length of a frustrum of a cone is machined onthe rear end of the atomizer head and is perpendicularly penetrated by abore 68 connecting the central bore 64 at the part of larger diameterthereof, with the space intermediate the inner and outer tubes 26, 28.The diameter of the bore 68 is somewhat greater than the diameter of thenarrow part of the central bore 64 and the diameter of the larger partof the central bore 64 is such that the cross-sectional area of thelarger part of bore 64 is equal to, or slightly less than, the sum ofthe cross-sectional area of the bore 68 and the cross-sectional area ofthe narrower part of bore 64, thereby assisting the mixing of streams ofoil and steam in the part of larger diameter of bore 64 and atomizationof oil which is supplied through the bore 68 and which intersects theaxis of the central passage 64 at an acute angle, thereby furtherassisting the mixing and atomization process.

In operation, steam is supplied to the interior of the inner tube 26 andoil is supplied to the space intermediate the inner and outer tubes 26,28 and pass through the respective bores to the peripherally arrangedstepped bores 56 and the central bore 64. The parts of larger diameterof the various stepped bores serve as mixing chambers in which the steamand oil are intimately mixed and from which the steam and oil mixture isdischarged as a finely atomized spray, the sprays from the peripherallyarranged stepped bores 56 combining to form a spray of approximatelyfrusto-conical form and the central passage discharging a stream ofatomized mixture axially of the burner barrel. The stream of mixturedischarged from the central passage 64 tends to stabilize the combinedflame adjacent the burner following ignition of the mixture from anadjacent burner when combustion air is discharged at relatively highvelocityfrom the air register 8 with little or no swirl impartedthereto. Furthermore the stream of mixture discharged from the centralpassage 64 substantially reduces any tendency for carbon deposits toform on the forward end of the atomizer head during operation of theburner.

In an alternative embodiment of the invention, not shown, the bore 68connecting the central passage 64 with the space intermediate the tubes26, 2.8 is omitted and steam alone is supplied to the central passagewhich is of constant diameter throughout. Such an arrangement alsosubstantially reduces any tendency for carbon deposits to form on theburner head during operation and also enhances stabilization of theflame after ignition from an adjacent burner.

It will be appreciated that, if desired, instead of oil other liquidfuels, such as, for example, naphtha, may be utilized and also thatinstead of steam, other elastic atomizing fluids, such as, for example,air may also be utilized. Furthermore the liquid fuel may be supplied tothe interior of the inner tube 26 and the elastic atomizing fluidssupplied to the space intermediate the inner and outer tubes 26, 28. Insuch an arrangement, where it was desired to supply elastic fluid aloneto the central passage 64, the passage is terminated short ofpenetrating the atomizer head and connects solely with the spaceintermediate the inner and outer tubes 26, 28 through the bore 68.

What is claimed is:

1. A liquid fuel atomizing assembly comprising a tubular barrel, meansdefining within said barrel a pair of separate passages extending thelength thereof, means for supplying liquid fuel to be atomized to one ofsaid passages extending the length thereof, means for supplying anelastic atomizing fluid to the other of said passages, a one pieceatomizer head connected to said barrel, said atomizer head includingmixing chambers distributed around the central axis of the head, thelongitudinal axis of said chambers diverging in the general direction ofdischarge, a central mixing chamber discharging along the central axisof the atomizer head, each chamber having a separate inlet duct forliquid fuel and a separate inlet duct for elastic atomizing fluid, saidducts being arranged to connect the chambers with said barrel passages,said central mixing chamber having an inlet duct for elastic atomizingfluid of greater cross-sectional area than the inlet duct for liquidfuel discharging thereto.

2. A liquid fuel atomizing assembly according to claim I 1 wherein thecross-sectional area of the central mixing chamber is equal to the sumof the cross-sectional areas of the inlet duct for liquid fuel and theinlet duct for elastic atomizing fluid discharging thereto.

3. A liquid fuel atomizing assembly according to claim 1 wherein theinlet duct for liquid fuel and the inlet duct for elastic atomizingfluid leading to the central mixing chamber are disposed at an acuteangle to each other.

4. A liquid fuel atomizing assembly according to claim 1 wherein saidatomizer head has a flat forward end face and includes a cylindricalbody having an internally threaded, central, well portion formed with anannular seat at the rearward end face thereof for engagement with acomplementary seat provided on a collar on the inner co-axial tube ofthe barrel, an outer, circumferential, flange formed with an annularseat at the rearward face thereof for engagement with a complementaryseat formed on the forward end face of the outer co-axial tube of thebarrel by the action of an associated cap nut co-acting with an externalthread on the forward end of the outer co-axial tube, a firstfrusto-conical surface formed as a chamber on the front end of thecylindrical body penetrated perpendicularly by stepped borescommunicating with a conical forward end of the well portion, a secondfrusto-conical surface at the rear end of the cylindrical body inregister with the space intermediate the inner and outer co-axial tubesof the barrel and penetrated perpendicularly with bores respectivelycommunicating with the stepped bores at the part of larger diameter anda central bore extending from the conical forward end of the wellportion to the front face of the cylindrical body.

5. A liquid fuel atomizing assembly according to claim 4 wherein saidatomizer head includes a third surface in the form of a part of afrustrum of a cone is provided at the rear end of the cylindrical bodyin register with the space intermediate the inner and outer co-axialtubes of the barrel and is penetrated perpendicularly by a borecommunicating with the central bore in an enlarged forward end portionthereof.

6. A liquid fuel atomizing assembly according to claim 1 wherein thecross-sectional area of the central mixing chamber is slightly less thanthe sum of the cross-sectional areas of the inlet duct for liquid fueland the inlet duct for elastic atomizing fluid discharging thereto.

References Cited UNITED STATES PATENTS 2,933,259 4/1960 Raskin 239-422 X2,942,790 6/1960 Starkey et al 239424 X 3,363,840 1/1968 Hall 239424.5 X

3,072,344 1/ i963 McKenzie 239433 FOREIGN PATENTS 1,259,910 3/1961France.

EVERETT W. 'KIRBY, Primary Examiner.

U .S. C1.IX.R.

